Influenza still represents one of the most dreadful human scourges. Complications associated to influenza infections are calculated to kill approximately 36,000 Americans every year. Vaccination and current anti-viral drugs have proven useful in preventing fatal complications upon influenza infection. However, the imminent evolution of new pandemic influenza strains likely to be resistant to current anti-viral drugs and the intrinsic technical limitations associated to current vaccine production methods underscore the urgent need to develop novel anti-influenza therapies. Anti-viral therapies that block or enhance cellular processes essential or detrimental for viral replication are significantly less prone to development of resistant viruses. Additionally, by affecting cellular pathways used by the virus, such therapies are more likely to work independently of the type, strain, and antigenic properties of the invading virus. Therefore, such therapies constitute ideal anti-influenza strategies. Here, we hypothesize that augmenting the activity of the sumoylation system, a cellular post-translational modification system, will inhibit influenza virus multiplication. The objective of this study is to evaluate the relevance of sumoylation for influenza virus infection, with the ultimate goal of determining whether the sumoylation system provides new targets for novel anti-influenza therapies. To this end, we will pursue two specific aims: (1) characterize the full array of influenza viral proteins that are sumoylated during infection, and (2) determine the effect of modulating the activity of the host cell sumoylation system on influenza virus multiplication. To achieve these goals, we will utilize a combination of proteomic methods, transient and stable transfection approaches, and adenovirus expression systems. The proposed assays will provide conclusive data on the effect of modulating sumoylation during influenza infections, and give meaningful hints to the effect of sumoylation on the life cycle of the virus. Additionally, the tools developed during the proposed studies will allow the effects of modulating the sumoylation system to be tested on other viruses. This research is highly innovative because the relevance of the sumoylation system for influenza and other viral infections remains unexplored. It is also of great urgency as it could lead to the development of novel anti-influenza therapies potentially applicable to the treatment of pandemic flu and other viral diseases. Furthermore, attaining the proposed goals will also provide the PI with the foundation and preliminary data required for crafting competitive NIH R01 proposals.